A police officer is approached by a man on the street who tells the officer that he was just robbed. Although he did not see where the robber fled, he knew the assailant's name and address, as the two men "grew up together." The officer and the victim went to the police station and completed an incident report. After a telephone call to one of the suspect's neighbors, they learned that he was at home. Must the officer obtain a warrant to make the arrest